Minimizing Broadcast Delay in Location-Based Channel Access Protocols

Location-based channel access protocols have been proposed as a means to broadcast safety related messages through inter-vehicle communications. The protocols divide the road into fixed-size cells and assign a channel to each cell. To broadcast, a vehicle would use the channel assigned to the cell it is currently traveling within. To improve bandwidth utilization, a vehicle may acquire channels dynamically from adjacent cells that are not occupied by other vehicles. In a TDMA setting where each channel is a time slot, message delay occurs as the vehicle must wait for the arrival of the next time slot it owns. This message delay time depends heavily on the adopted cell-to-channel mapping function. We examine an existed naive channel allocation scheme and proposed three new ones. An analysis shows that the proposed schemes may reduce the delay by 50% to 90% .